Preparation of lower chlorides of molybdenum and tungsten



PREPARATION OF LOWER CHLORIDES F IVIOLYBDENUM AND TUNGSTEN Seymour Senderoif, Chevy Chase, Md and Roger J. Labrie, North Attleboro, Mass., assignors to the United States of America as represented by the Secretary of Commerce No Drawing. Application January 22, 1954, Serial No. 465,666

3 Claims. (Cl. 2387) The present invention relates to the preparation of the lower chlorides of molybdenum and tungsten and in particular to the use of saturated aliphatic hydrocarbons containing between and 50 carbon atoms per molecule as a reducing agent for the higher chlorides of molybdenum and tungsten.

When the metals (or their compounds) of group VI-B of the periodic system (i. e., chromium, molybdenum, and tungsten) are chlorinated with an excess of chlorine, chromium forms the trichloride, but molybdenum and tungsten form the pentachloride and hexachloride respectively. There is no satisfactory way at present to obtain the lower chlorides of these two elements from the higher chloride produced by chlorination. Laboratory methods, such as hydrogen reduction or thermal dissociation involve high temperature gas-phase reactions which are diflicult to control and which result in products which are highly polymerized and highly inert to further chemical treattnent. Reduction in aqueous solutions gives hydrated compounds from which the water cannot be removed without decomposing the compounds, or complex compounds which are expensive and difiicult to make. At present the lower chlorides of molybdenum and tungsten are, as far as the inventors can determine, not commercially available.

The anhydrous lower chlorides of molybdenum, particularly the trichloride, are important as a source of molybdenum for use in the electrolytic preparation of molybdenum metal from fused salt electrolytes, in a process such as that described in copending application Ser. No. 268,324, filed by Seymour Senderolf and Abner Brenner on January 25, 1952.

It is an object of the present invention to provide a rapid and cheap method of reducing the higher chlorides of molybdenum and tungsten.

It is another object of the present invention to provide a method of reducing the higher chlorides of molybdenum and tungsten by means of a cheap reducing agent.

It is another object of the present invention to provide a method of reducing the higher chlorides of molybdenum and tungsten at moderate temperatures.

it is another object of the present invention to provide lower chlorides of molybdenum and tungsten which are amenable to further chemical treatment.

Still another object of the present invention is to provide a method for producing lower chlorides of molybdenum and tungsten, which method yields useful byproducts.

Another object of the present invention is to provide a method for economically producing molybdenum trichloride.

Another object of the present invention is to provide lower chlorides of molybdenum and tungsten which may readily be reduced to still lower chlorides.

Other uses and advantages of the invention will become apparent upon reference to the specification.

According to the present invention the higher chlorides of molybdenum and tungsten are reacted with suitable saturated aliphatic hydrocarbons to produce the lower 2,715,058 Patented Aug. 9, 1955 metal chlorides, chlorinated parafiins and anhydrous hydrogen chloride gas. Since the higher metal halides are practically insoluble in the hydrocarbons of low molecular weight, it is preferable to use hydrocarbons containing from 10 to 50 carbon atoms per molecule in which the higher chlorides are more readily soluble. The reaction must be conducted in an inert atmosphere since these metal chlorides decompose in air. The temperature to which the mixture must be heated depends upon the rate of the reaction desired. As long as the mixture is above the melting point of the hydrocarbon some reaction, although in most cases an extremely slOW reaction, occurs. The temperatures for optimum results depend upon the particular paraflin hydrocarbon used, as indicated in the examples below. The maximum temperature is the boiling point of the hydrocarbon.

The method of the present invention produces lower chlorides which are amenable to further chemical treatment and in addition produces commercially valuable byproducts such as anhydrous hydrogen chloride. The excess hydrocarbon and other organic compounds are washed away with a hydrocarbon solvent which is removed by warming well below the reaction temperature. This leaves a fine black powder which is unstable in air. in the case of molybdenum the atomic ratio of molybdenum to chlorine in this powder is close to 1:4. In the case of tungsten the ratio is between 1:4 and 1:5. The powder may be heated to produce still lower chlorides. If heated between 250 degrees to 300 degrees C., molybdenum trichloride will be produced. Below 250 degrees C. the reaction is so slow as to be economically impractical, while just above 300 degrees C., minute quantities of molybdenum dichloride are formed. At 600 degrees C. the black powder is rapidly converted to molybdenum dichloride.

The following are typical examples of the reaction which demonstrate the application of the invention.

1. 40 g. of MOC15 are added to 200 g. of paraflin wax in a large test tube in an inert atmosphere. This mixture is then heated with continuous stirring to a temperature between the melting point and boiling point of the hydrocarbon and high enough to initiate the reaction. In this case a temperature of C. was used. When the reddish color of the dissolved MoCls has disappeared in the reaction mixture and ebullition of HCl has ceased, the reaction is complete and the mixture is allowed to cool. The excess parafiin and the other organic compounds formed are washed away with high boiling petroleum ether to leave a fine black powder. The reduced molybdenum compound is unstable in air, hence this washing must be carried out in an inert atmosphere. The product obtained has an atomic ratio of MozCl which is close to 1:4. The product may be heated in an inert atmosphere at 275 degrees C. to produce molybdenum trichloride (MoCls).

2. 40 g. of M0Cl5 are added to 200 ml. of cetane in a large test tube in an inert atmosphere. This mixture is then heated with continuous stirring to a temperature between the melting point and boiling point of the hydrocarbon and high enough to initiate the reaction. In this case, a temperature of C. was used. When the reddish color of the dissolved MoCls has disappeared in the reaction mixture and ebullition of HCl gas ceases, the reaction is complete and the mixture is allowed to cool. The excess cetane and the other organic compounds tormed are washed away. The product obtained has an atomic ratio of MozCl which is close to 1:4. The product may be heated in an inert atmosphere at 275 C. to produce molybdenum trichloride (MoCla).

3. 40 g. of WCle are added to 200 ml. of refined cetane in a large test tube in an inert atmosphere. This mixture is stirred continuously and heated to C. When the red color is gone and gas ebullition has stopped, the mixture is cooled and the excess cetane and by-products are washed away with petroleum ether in an inert atmosphere to separate the reduced tungsten compound. The atomic ratio of WzCl in the final product is between 1:4 and 1:5.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made within the scope of our invention as defined in the appended claims.

What is claimed is:

l. The method of reducing the higher chlorides of molybdenum and tungsten comprising mixing a metal chloride selected from the group consisting of molybdenum pentachloride and tungsten hexachloride with a saturated aliphatic hydrocarbon having at least ten carbon atoms per molecule, heating the mixture in an inert atmosphere to a temperature in the range between the melting point and boiling point of said saturated aliphatic hydrocarbon, said heating continuing until the ebullition of hydrogen chloride has substantially ceased, and washing the reaction products with a hydrocarbon solvent to leave a fine black powder.

2. The invention according to claim 1 in which said powder is heated in an inert atmosphere to at least 250 degrees C.

3. The invention according to claim 1 in which the saturated aliphatic hydrocarbon contains from 10 to 50 carbon atoms per molecule.

4. The method of reducing molybdenum pentachloride and tungsten hexachloride to lower chlorides which comprises mixing one of said chlorides with a saturated aliphatic hydrocarbon having at least ten carbon atoms per molecule, heating the mixture in an inert atmosphere to a temperature in the range between the melting point and boiling point of said saturated aliphatic hydrocarbon, said heating continuing until the ebullition of hydrogen chloride has substantially ceased, and washing the reaction products with a hydrocarbon solvent to leave a fine black powder.

5. The method of reducing molybdenum pentachloride to a lower chloride which comprises mixing molybdenum pentachloride with a saturated aliphatic hydrocarbon having at least 10 carbon atoms per molecule, heating the mixture in an inert atmosphere to a temperature in the range between the melting point and boiling point of said saturated aliphatic hydrocarbon, said heating continuing until the ebullition of hydrogen chloride has substantially ceased, and washing the reaction products with a hydrocarbon solvent to leave a fine black powder.

6. The invention according to claim 5 in which said powder is heated in an inert atmosphere to at least 250 degrees C. to produce molybdenum trichloride.

7. The invention according to claim 5 in which the saturated aliphatic hydrocarbon contains from 10 to 50 carbon atoms per molecule.

8. The method of reducing tungsten hexachloride to a lower chloride which comprises mixing tungsten hexachloride With a saturated aliphatic hydrocarbon having at least ten carbon atoms per molecule, heating the mixture in an inert atmosphere to a temperature in the range between the melting point and boiling point of said saturated aliphatic hydrocarbon, said heating continuing until the ebullition of hydrogen chloride has substantially ceased, and washing the reaction products with a hydrocarbon solvent to leave a fine black powder.

No references cited. 

1. THE METHOD OF REDUCING THE HIGHER CHLORIDES OF MOLYBDENUM AND TUNGSTEN CONPRISING MIXING A METAL CHLORIDE SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM PENTACHLORIDE AND TUNGSTEN HEXACHLORIDE WITH A SATURATED ALIPHATIC HYDROCARBON HAVING AT LEAST TEN CARBON ATOMS PER MOLECULE, HEATING THE MIXTURE IN AN INERT ATMOSPHERE TO A TEMPERATURE IN THE RANGE BETWEEN THE MELTING POINT AND BOILING POINT OF SAID SATURATED ALIPHATIC HYDROCARBON, SAID HEATING CONTINUING UNTIL THE EBULLITION OF HYDROGEN CHLORIDE HAS SUBSTANTIALLY CEASED, AND WASHING THE REACTION PRODUCTS WITH A HYDROCARBON SOLVENT TO LEAVE A FINE BLACK POWDER. 